What Is A CDN? A Beginner’s Guide To Content Delivery Networks

Almost everyone has heard of the importance of site speed, even the average blogger with lackluster technical skills.

However, not everyone is aware of what a CDN is and how it goes hand in hand with site speed.

Here are a few common questions site owners ask in regard to CDNs:

“What is a CDN?”

“What are the benefits of a CDN?”

“Do I still need to purchase hosting if I have a CDN?”

“Does my site need a CDN?”

We’re going to go over what a CDN is and thoroughly explain the important role this technology plays in the modern web.

We’ll also briefly touch base on the differences between your web server and a CDN before placing our focus on who does and does not need this technology implemented on their website.

What is a CDN?

Here’s the technical definition of a CDN, or at least a paraphrased version of it. A CDN, which stands for Content Delivery Network, is a global network of servers that deliver content to visitors of a website based on where that visitor is located.

You need to understand how regular web hosting works in order to understand this definition as well as the importance of it. In a typical web hosting environment, all of the traffic running to your website gets sent to your host’s web server, the one you installed your site on and the one that holds its data.

This often results in a slower website for all visitors as that single server struggles to stay afloat among the surge of traffic it receives on a regular basis. It can even leave your site vulnerable to DDoS attacks. Why is this bad? Here are a few quick facts to help you understand the importance of having your site run as quickly and reliably as possible:

40% of consumers abandon a website that takes more than 3 seconds to load. [Source: Kissmetrics via Akamai and Gomez.com]

79% of shoppers who are dissatisfied with website performance are less likely to buy from the same site again. [Source: Kissmetrics via Akamai and Gomez.com]

52% of online shoppers state quick page loading is important to their site loyalty. [Source: Kissmetrics via Akamai and Gomez.com]

A 1-second delay in page response can result in a 7% reduction in conversions. [Source: Kissmetrics via Akamai and Gomez.com]

This, obviously, leads us to our next question.

What are the benefits of a CDN?

The most obvious and most important benefit of a CDN is an increase in site speed for all users of your website no matter where they’re located in the world. When you implement a CDN on your website, you’re distributing access to it to what are known as “proxy servers” located all around the world.

Let’s say the web server you purchased from your host is located in New York and you do not use a CDN. In this environment, a visitor from Australia would need to load all of the static content on your website, which are your images, CSS stylesheets, and JavaScript files, from New York, which can take quite a bit of time.

If you use a CDN, your Australian user would be able to load that static content from a server that’s closest to them, maybe even in the same country depending on the CDN service you decide to go with. This will allow them to load the page in a much quicker manner.

You can see how this works in the illustration above. You still have your “origin server,” which is storing your WordPress installation and database, but you also have your “replicated web-server clusters,” which store your site’s static content. Again, static content are images, videos, CSS stylesheets, and JavaScript files.

The origin server is located toward the south of North America in the illustration above while the replicated web-server clusters are located in six continents around the world. You can see how the “user” icons demonstrate how users are served static content from the replicated web servers closest to them instead.

The impact? Some sites report seeing a decrease of more than 50% in the amount of time it takes for their site to load after implementing a CDN. [Source: KeyCDN]

If you’re still having a tough time figuring out how this technology makes your website faster, think of it like a highway:

The main lane is your origin server.

The additional lanes are your replicated web servers.

The cars are the users visiting your website.

Without those additional lanes, all of the cars on the road need to use the main lane. This will eventually result in a traffic jam as more and more cars fill the lane. Traffic will start to slow before the flow stops altogether after the lane becomes too congested.

If you open those additional lanes, cars will be able to distribute themselves among them rather than relying on a single lane. This will allow them to move at a much quicker pace, and they’ll get to their destination a lot faster than they would have if they were all using the same lane.

In other words, having your users load static content from a server that’s closest to where they’re located will allow each and every one of them to load your website much quicker than they’d be able to if they were all loading that content from the same server.

Security – The other main benefit of a CDN

Take a look at the illustration above. It shows you that real visitors, the “legitimate traffic” icon, are not the only ones who will load your website from the servers your CDN gives your site access to. Hackers, bots, spammers, and fake traffic sent from DDoS attacks will land on these servers as well, which means your CDN will block attacks and prevent them from affecting your origin server, the place where your site’s most vulnerable files are stored.

Even if they do manage to take down one of your proxy servers, service will only affect that individual server. Users will still be able to access your site through the other servers.

Cheaper web hosting

This is another benefit of using a CDN. Requiring users to load static content from a single server uses up a lot of resources and bandwidth. Offloading these tasks to your CDN can reduce the amount of bandwidth you use on the server your website is hosted on, which may reduce your web hosting costs. You’ll still need to pay for the CDN service, though, so keep that in mind.

The differences between a web host and a CDN

Here’s an answer to the question “do I still need to purchase web hosting if I have a CDN?” The short answer is “yes,” but let’s elaborate. Only certain content is served from the proxy servers your CDN gives you access to, this content typically being images and other media, CSS stylesheets, and JavaScript files, as stated before. That means you still need a main server to host the rest of your site on.

In short…

A traditional web host provides a server for you to host your entire website on.

A CDN gives you several proxy servers around the world for you to serve static content from.

A CDN is designed to complement a traditional web server by enhancing the performance of the site being hosted on it. Without a traditional web server, there is no site for a CDN to enhance.

Does your site need a CDN?

We’ve thoroughly explained the benefits of using a CDN and how most websites will only see improvements in the way they perform after implementing this technology, but does every site need a CDN, and more importantly, does yours?

Believe it or not, there are a few different types of websites that would benefit very little from this type of service. Let’s talk about them so you can make an educated decision on whether or not your site would benefit from the added cost of using a CDN.

Consider these factors.

Do you have a traffic-heavy site?

This is one of the biggest factors you need to consider if you’re thinking about implementing a CDN for your website. Traffic-heavy websites are more likely to experience downtime than other sites as the servers that run them have trouble supporting the heavy load.

If you have a traffic-heavy website, consider implementing a CDN to help distribute that traffic to servers located around the world rather than forcing your origin server to handle it all. You should also consider upgrading to a cloud-hosting solution if you haven’t already as servers in this type of infrastructure have the ability to scale as needed.

Do you expect your business to grow rapidly?

This factor ties into the last one. Your site may not experience heavy traffic now, but if you expect your business to grow rapidly at all, you may want to consider implementing a CDN and, again, upgrading to a cloud-hosting solution.

If you’re about to launch a product and expect to do promotion for it that will likely drive a lot of traffic to your site, you need to be ready. A launch of this nature relies on the uptime of your website. If you don’t upgrade the infrastructure your site is using before you launch, you may experience nothing but downtime as all of that traffic comes flooding in.

Do you have a small website?

This is a great factor to consider. If you have a small website that doesn’t have a lot of pages, doesn’t use a lot of images and doesn’t experience heavy traffic on a regular basis, you likely won’t experience a dramatic improvement in site performance if you choose to use a CDN. Feel free to keep an eye on things, but don’t make it a priority just yet.

Does your site use a lot of media items (images, videos, etc.)?

This is a major factor to consider. When a user visits your website, they need to load every image and resource on the page. You can do a lot to help your site by optimizing images, offloading WordPress media items to a cloud-storage solution, such as Amazon S3, and implementing lazy loading, but you can do more by using a CDN.

Consider implementing this technology if you have an active blog that uses images in every post or you use a lot of high-quality images throughout your site. Photographers, for example, often use unoptimized versions of their images to fill out their portfolios. Understandable, but it can lead to a slow website nonetheless.

Does your website target local traffic?

This is another thing to consider. CDNs are meant to work on a global scale, helping users load your site more quickly by loading resources from a server that’s closest to them. However, if you have a local site, such as a website for a local, brick-and-mortar business, your traffic is likely local as well, which means a CDN wouldn’t make much sense for your business.

Does your site experience downtime?

This one kind of ties into the last points. You may have already experienced issues with your site, such as downtime, excessive load times, and actual complaints from customers stating your site is too slow. You can use tools like Pingdom and Uptime Robot to monitor the performance of your site. If you’re experiencing issues, consult your host first. If you have a global audience, a traffic-heavy site and use a lot of images, consider implementing a CDN.

Final thoughts

CDNs play a vital role in keeping a site running as quick and smooth as it possibly can. Many businesses rely on this technology to keep their sites and services afloat through heavy surges of traffic, even 75% of the top 100 websites, according to the Radware Blog.

Let’s roundup the factors your site should have if you want to add CDN services to it.

You should consider implementing a CDN if…

You have a traffic-heavy site.

You expect your business to grow and cause huge spikes in traffic.

You use a lot of media items, especially images.

You attract visitors from all around the world.

You experience issues with site performance.

You should not consider implementing a CDN if…

You have a local website.

You have a small website.

You don’t have a lot of traffic.

You don’t use a lot of media items.

If you’ve decided to use this technology on your site, check out our posts about popular CDN services MaxCDN and KeyCDN.

If you’re running on a tight budget, there are free CDN services such as Cloudflare you can try. Otherwise, check out these posts to learn how to optimize a WordPress site for performance: